If I were going to do a lesson on the salt marshes, I would present the work
of Martin Johnson Heade as inspiration. He painted the marshes of Mass. and
RI and the paintings are stunning. There is a show of his now at the
National Gallery so maybe you could get some images from the NGA web site.
When I saw the show in Boston, I bought the catalogue which has beautiful
images. You could use his paintings to teach one point as well as
atmospheric perspective.
Marian